JP3587452B2 - Data reception device and data reception control method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data reception device and a data reception control method, and more particularly, to an improvement in a data reception device that controls a reception data error in data communication by making a retransmission request to the data transmission device.
[0002]
[Prior art]
An ARQ (Automatic Repeat Request, automatic retransmission request) method is one of the methods for removing an error that occurs during data transmission between transmitting and receiving apparatuses. ARQ is a control method for retransmitting a data unit (frame) containing an error and removing the error. ARQ is described in detail in "Automatic Repeat Request Error-Control Schemes" (Shu Lin et al., IEEE Commun. Mag., Vol. 22, No. 12, Dec. '84).
[0003]
FIG. 14 is a timing chart schematically showing the basic operation of ARQ. In the figure, (a) is input data to the data transmission device, (b) is data stored in the transmission buffer of the data transmission device, (c) is a transmission frame from the data transmission device, and (d) is data reception. (E) is the sequence number of the frame stored in the retransmission request buffer of the data receiving apparatus, (f) is the data stored in the receiving buffer of the data receiving apparatus, and (g) is the data receiving frame. This is the received data output by the device.
[0004]
The mark x in the received frame (d) indicates a reception failure. Further, an arrow from the reception frame (d) to the transmission frame (c) indicates a backward line from the reception device, P of P1 on the arrow indicates Positive Acknowledgement, and a reception failure occurs in the reception frame. Not indicate. N such as N2 and N4 indicates Negative Acknowledgement, and indicates that a reception failure has occurred in the received frame. P1 means confirmation of response to the frame of sequence number 1, N2 means non-response of the frame of sequence number 2, and is a retransmission request for the frame of sequence number 2.
[0005]
First, the operation on the transmitting side will be described. When there is data input, the transmission device divides the input data into frames, which are transmission units, and stores the data in a transmission buffer. If there is no retransmission request from the receiving device at the transmission timing, the transmitting device extracts data in frame units in the transmission buffer in the order of storage, performs transmission processing such as error detection coding, and then transmits the data as a transmission frame. On the other hand, when a retransmission request is received from the receiving device, the requested retransmission frame is inserted into the transmission frame, so that a stagnation shown in FIG. 14B occurs in the transmission buffer.
[0006]
Next, the operation on the receiving side will be described. The receiving apparatus performs error detection on the received frame, and if no error is detected, stores the error in the reception buffer. On the other hand, if an error is detected in the received frame as a result of the error detection, the sequence number of the frame is stored in the retransmission request buffer until a retransmission request is sent for the error frame. In the case of FIG. 14, when a retransmission request (N2 or the like) is transmitted, it is not necessary to store it, so that it is not stored in the retransmission request buffer. If another retransmission request occurs until a correct retransmission is received, it is stored. Here, the time difference from the transmission frame to the reception is displayed as two frames. The receiving buffer outputs the received data as received data when the received frames are arranged in the receiving buffer according to the sequence number.
[0007]
FIG. 15 is a block diagram showing a configuration example of a conventional general data transmission apparatus (ARQ transmission apparatus). In the figure, 1 is a retransmission request determination unit, 2 is a transmission buffer unit, 3 is a transmission processing unit, 4 is a retransmission buffer unit, and 5 is a logical sum operation unit. Also, i1 is a backward signal, i2 is generated data, s1 is a retransmission request signal, s2 is a generated data block, s3 is a generated frame, s4 is a retransmission frame, and s5 is a transmission frame.
[0008]
Upon confirming a retransmission request from the receiving device based on the backward signal i1, the retransmission request determination unit 1 outputs a retransmission request signal s1. The transmission buffer unit 2 divides the generated data i2 into data blocks in frame units and stores them. The transmission buffer unit 2 outputs the internal data blocks as the generated data block s2 in the order of storage, but stops the output of the generated data block s2 when the retransmission request signal s1 is confirmed. When the generated data block s2 is input, the transmission processing unit 3 performs a framing process such as error detection coding and outputs a generated frame s3. The retransmission buffer unit 4 stores a copy of the transmission frame until a response to the transmission frame is confirmed. Also, it outputs a retransmission frame s4 according to the retransmission request signal s1. The OR operation unit 5 outputs one of the generated frame s3 and the retransmission frame s4 controlled based on the retransmission request signal s1 as a transmission frame s5.
[0009]
FIG. 16 is a block diagram showing a configuration example of a conventional general data receiving device (ARQ receiving device). In the figure, 6 is an error detection unit, 7L is a reception buffer unit, 8L is a sequence number storage unit, 9L is a retransmission request buffer unit, and 10 is a backward signal generation unit. Also, i3 is a received frame, s6a is a significant frame, s6b is an error detection sequence number, s7a is received data, s8 is a response confirmation sequence number, s9a is a retransmission request sequence number, and s10 is a response confirmation frame or a retransmission request frame.
[0010]
The error detection unit 6 detects an error in the received frame i3, and outputs a significant frame s6a if no error is detected. When an error is detected in the received frame i3, the sequence number of the error frame is output as an error detection sequence number s6b. The reception buffer unit 7L stores therein the input significant frame s6a. When the order numbers of the significant frames are aligned, the data part is extracted and sequentially output as the received data s7a.
[0011]
The sequence number storage unit 8L extracts the sequence number of the significant frame s6a. If this value is larger than the previously stored sequence number, the response confirmation sequence number s8 is updated to the sequence number. The retransmission request buffer unit 9L outputs the minimum value among the input error detection sequence numbers s6b as the retransmission request sequence number s9a. If the retransmission request sequence number s9a is input, the backward signal generation unit 10 outputs a retransmission request for the frame. If the signal s9a is not input, the backward signal generation unit 10 performs a response confirmation corresponding to the response confirmation sequence number s8. Output.
[0012]
FIG. 17 is a block diagram showing a detailed configuration example of the transmission buffer unit 2 of FIG. In the figure, 11 is a data division unit, 12 is a write control unit, 13 is a read control unit, and 141 to 14n are buffers. Further, s1 is a retransmission request signal, i2 is generated data, s2 is a generated data block, s11 is a data block, s12a is buffer head position information, s12b is write position information, and s13 is read position information.
[0013]
The data division unit 11 divides the generated data i2 input from the outside into data blocks in frame units, and outputs a data block s11. The write control unit 12 outputs the write position information s12b and selects the write position of the data block s11 from the buffers 141 to 14n. The write control unit 12 updates the oldest write buffer position based on the read position information s13, and notifies the read control unit 13 of the position using the buffer head position information s12a.
[0014]
The read control unit 13 selects a buffer position to be read from the buffers 141 to 14n based on the buffer head position information s12a, and outputs the generated data block s2 from the transmission buffer unit 2. However, when the retransmission request signal s1 is input, control is performed so that the generated data block s2 is not output. As described above, the transmission buffer unit 2 cannot output a newly generated data block when there is a retransmission request. For this reason, if retransmission requests occur frequently, the number of data blocks reserved inside the transmission buffer unit 2 increases, which causes a delay occurring between the transmitting and receiving apparatuses.
[0015]
FIG. 18 is a timing chart showing an example of the operation of the transmission buffer unit 2 of FIG. 17, and is a diagram for explaining a delay occurring in the transmission buffer unit of the conventional data transmission device. In the figure, (a) is a retransmission request signal s1, (b) is generated data i2, (c) is data stored in the transmission buffers 141 to 14n, and (d) is a generated data block s2. Further, d1 to d3 indicate data blocks, respectively.
[0016]
It is assumed that no delay has occurred in the data block d1. FIG. 18 shows a case where the data block d2 is retained in the buffer due to the occurrence of the retransmission request signal s1 due to the occurrence of an error, and a delay corresponding to two data blocks has occurred. In this case, three data are accumulated in the transmission buffers 141 to 14n, and after the retransmitted DB2 is output as the generated data block s2, if there is no subsequent data, the data is finally reduced. Thus, the data block d3 has a delay corresponding to two data blocks because there is a data block reserved by a retransmission request that has occurred previously. As described above, the influence of the delay due to the retransmission request in the block affects data blocks after the occurrence point.
[0017]
FIG. 19 is a block diagram showing a detailed configuration example of the reception buffer unit (the reception buffer unit 7L in FIG. 16) of the conventional data receiving device. In the figure, 21 is a data extraction unit, 22 is a write control unit, 23L is a read control unit, 24 is a sequence number storage unit, and 251 to 25n are buffers. S6a is a significant frame, s7a is received data, s21a is a significant frame number, s21b is a data block, s22a is buffer top position information, s22b is write position information, s23 is read position information, and s24 is an output frame number. .
[0018]
The data extraction unit 21 extracts a sequence number and a data block from the significant frame s6a and outputs a significant frame number s21a and a data block s21b. The write control unit 22 selects a write buffer from the relative value between the significant frame number s21a and the sequence number of the data block stored in the first buffer, and outputs the write position information s22b.
[0019]
The read control unit 23L can know the frame number of the received data s7a output from this block from the output frame number s24. The reading control unit 23L starts reading control from the buffer when the sequence number of the data block stored in the first buffer is larger than the output frame number s24 by one. Reading is performed until an empty buffer is detected. The read control unit 23L outputs read position information s23 according to the above control. The sequence number storage unit 24 stores the sequence number of the data block output last according to the operation of the read control unit 23L.
[0020]
The buffers 251 to 25n store the data block s21b according to the write position information s22b, and output the received data s7a according to the read position information s23. As described above, the reception buffer unit 7L reserves the data blocks of the received frame without error until the sequence numbers are aligned. Therefore, when the retransmission of an arbitrary frame occurs continuously or when retransmission frequently occurs, the delay of the data block reserved in the reception buffer unit 7L increases.
[0021]
FIG. 20 is a timing chart showing an example of the operation of the reception buffer unit 7L of FIG. 19, and is a diagram for explaining a delay occurring in the reception buffer unit of the conventional data receiving device. In the figure, (a) shows the received frame i3, (b) shows the data stored in the receiving buffers 251 to 25n, (c) shows the output frame s24, and (d) shows the received data s7a. In addition, f1 to f5 each indicate a reception frame. 1 to 10 in a rectangular frame represent each data block, and the same numbers represent the same data blocks. Also, the number of the received frame indicates the sequence number.
[0022]
Here, it is assumed that an error has occurred in the reception frames f2 and f4. Since the received frame f1 arrives according to the sequence number, no delay occurs in the block. The received frame f2 is not stored in the buffer because an error has occurred. The reception frame f3 is stored in the reception buffers 251 to 25n because the frame having the sequence number 2 is not output as the reception data. The frame is retained in the reception buffer until the reception frame having the sequence number 2 is received without error. Therefore, the data is output as reception data after waiting for the reception frame f5, and a delay corresponding to 7 reception frames occurs in the reception buffer unit 7L.
[0023]
FIG. 21 is a block diagram illustrating a detailed configuration example of a retransmission request buffer unit (request buffer 9L in FIG. 16) of the conventional data receiving apparatus. In the figure, 31 is a write control unit, 32L is a read control unit, and 331 to 33n are buffers. Also, s6b is an error detection order number, s9a is a retransmission request order number, s31a is buffer head position information, s31b is write position information, and s32 is read position information.
[0024]
Here, the write control unit 31 and the read control unit 32, and the buffer head position information s31a, the write position information s31b, and the read position information s32 are respectively written in the write control unit 12, the read control unit 13, and the buffer in FIG. Since they are the same as the start position information s12a, the write position information s12b, and the read position information s13, the description is omitted. The buffers 331 to 33n input the error detection order number s6b according to the write position information s31b. Further, it outputs a retransmission request sequence number s9a according to the read position information s32.
[0025]
FIG. 22 is a timing chart showing an example of the overall operation of a conventional general data receiving device (ARQ receiving device in FIG. 16), and is a diagram for describing a delay caused by an increase in retransmission requests. In the figure, (a) shows the received frame i3, (b) shows the data stored in the reception buffers 251 to 25n, (c) shows the data stored in the retransmission request buffers 331 to 33n, and (d) shows the received data s7a. Further, f1 to f6 each indicate a reception frame. 1 to 13 in the square frame represent each data block, and the same numbers represent the same data blocks. Also, the number of the received frame indicates the sequence number.
[0026]
Here, it is assumed that an error has occurred in the reception frames f2, f4, and f5. Since the received frame f1 arrives according to the sequence number, no delay occurs. The reception frame f3 is stored in the reception buffer until the frame of the sequence number 2 is received without error, so that a delay equivalent to four reception frames occurs. On the other hand, the reception frame f6 is stored in the reception buffer until the frames of sequence numbers 6 and 8 are received without error, so that a delay corresponding to 5 reception frames occurs.
[0027]
In the error control method based on the conventional ARQ, retransmission is continued until an error in a frame is eliminated in order to transmit data without error between a transmitting device and a receiving device. Therefore, the above-mentioned method has a problem that when retransmission frequently occurs due to deterioration of the line state, a delay generated between transmission and reception increases.
[0028]
In order to solve this problem, according to a predetermined condition, retransmission of an error frame is stopped, and a frame that has stayed in a reception buffer as a significant reception frame by the time the retransmission is stopped is used as reception data. There is a retransmission control method that suppresses the occurrence of delay and delay dispersion by taking out.
[0029]
As an example of such a retransmission control method, there is a document “Transmission device and reception device for data transmission accompanied by retransmission request” (Japanese Patent Laid-Open No. 11-88466). In this document, a threshold value is set for the number of frames stored in the retransmission request buffer, and if an error occurs beyond this threshold value, the number of frames corresponding to the frame number stored in the retransmission request buffer up to that time is set. A method of stopping the retransmission request and extracting the received data is adopted.
[0030]
FIG. 23 is a block diagram showing another configuration example of a conventional data transmission receiving device (ARQ receiving device), and is a diagram for describing a retransmission stop function described in the above publication. In the figure, 7 is a reception buffer unit, 8 is a sequence number storage unit, and 9 is a retransmission request buffer. S9b is a discard order number. Other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0031]
The retransmission request buffer unit 9 outputs the minimum value among the input error detection sequence numbers s6b as the retransmission request sequence number s9a. Further, the retransmission request buffer unit 9 monitors the buffer amount, and when the buffer amount exceeds the reference value, stops the retransmission request for the stored sequence number. Specifically, it outputs the discard sequence number s9b and notifies the sequence number storage unit 8 and the reception buffer unit 7. The sequence number storage unit 8 updates the response confirmation sequence number s8 when the discard sequence number s9b is larger than the response confirmation sequence number s8. When outputting the received data s7a, the reception buffer unit 7 outputs the data block in the buffer as discarding the unacknowledged confirmation data block having the sequence number smaller than the discard sequence number s9b.
[0032]
FIG. 24 is a block diagram showing a detailed configuration example of a retransmission request buffer unit (retransmission request buffer unit 9 in FIG. 23) of a conventional data receiving apparatus having a retransmission stop function. In the figure, 32 is a read control unit, 34 is a buffer amount monitoring unit, s9b is a discard sequence number, s331 to s33n are buffer data, and s34 is read control information. Other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0033]
The buffer amount monitoring unit 34 monitors the number of retransmission requests stored in the buffers 331 to 33n, and when this value exceeds the upper limit, stops all retransmission requests stored in the buffer. More specifically, read control information s34 is output, and the read operation of read control unit 32 is stopped. Further, the buffer amount monitoring unit 34 outputs the maximum value of the sequence number among the stopped retransmission requests as s9b.
[0034]
FIG. 25 is a block diagram showing a detailed configuration example of a reception buffer unit (reception buffer unit 7 in FIG. 23) of a conventional data reception device having a retransmission stop function. In the figure, reference numeral 23 denotes a read control unit, and s9b denotes a discard sequence number. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0035]
If the discard sequence number s9b has not been input, the read control unit 23 operates in the same manner as in FIG. When the discarding sequence number s9b is input, the reading control unit 23 does not wait for retransmission of a frame having a sequence number smaller than the discarding sequence number s9b, and performs a reading operation on the assumption that the corresponding frame is discarded. Do.
[0036]
FIG. 26 is a timing chart showing an example of the operation of the entire conventional data receiving apparatus having the retransmission stop function (ARQ receiving apparatus in FIG. 23). In the figure, (a) shows the received frame i3, (b) shows the data stored in the reception buffers 251 to 25n, (c) shows the data stored in the retransmission request buffers 331 to 33n, and (d) shows the received data s7a. Further, f1 to f6 each indicate a reception frame.
[0037]
This figure shows the operation when an error of the same condition as in FIG. 22 occurs. That is, it is assumed that an error has occurred in the reception frames f2, f4, and f5. In the timing explanatory diagram of FIG. 26, the reason that no delay occurs in the received frame f1 is that there is no error so that the received frame f1 is output directly, for the same reason as in FIG. When an error is detected in the reception frame f2, data is accumulated in the reception buffer until the frame of the sequence number 2 is received without error.
[0038]
Here, it is assumed that the upper limit of the reservation is 0. In this case, even if an error is detected in the received frame f4 and an error is further detected in the received frame f5 before receiving a correct retransmission of the sequence number 4, no retransmission is requested by the control of the retransmission request buffer. Therefore, the received frame f6 is output as received data without waiting for the frames of sequence numbers 6 and 8 to be retransmitted correctly, and the delay is equivalent to one received frame.
[0039]
[Problems to be solved by the invention]
For example, in multimedia mobile communication that provides various services in an integrated manner, various transmission qualities are required from real-time services such as voice to services premised on error-free transmission such as file transfer and data communication. In general, the quality of a transmission line of a wireless line is lower than that of a wired line, and a temporal change in the state is severe.
[0040]
However, in the method of stopping the retransmission of the data receiving apparatus described in the related art, since the stopping condition is fixed, it cannot function effectively on a wireless communication line where time changes drastically due to the effects of fading, shadowing, and the like. In some cases, the delay amount and the error rate may not satisfy the transmission quality requirements.
[0041]
Also, in the retransmission stop method described above, since the stop condition is fixed, it does not function effectively for a service in which the amount of data received per unit time changes. May not satisfy the transmission quality requirements.
[0042]
The present invention has been made in view of the above circumstances, and provides a data reception device and a data reception control method for performing control for suppressing the accumulation time of each data block in a reception buffer according to various conditions and requests. The purpose is to do. In particular, it is an object of the present invention to provide a data receiving apparatus and a data receiving control method for controlling output delay of received data and errors remaining in the received data according to a line state, a line quality, a received data amount, and the like.
[0043]
[Means for Solving the Problems]
A data receiving apparatus according to claim 1, wherein the data receiving apparatus outputs a request for retransmission of an error frame to the data transmitting apparatus based on an error detection result of the received frame. A reception buffer that stores a data block corresponding to a significant frame until receiving a received frame, and outputs a stored data block based on a discard control signal, and an order of other error frames until a retransmission frame is received for a preceding error frame. A retransmission request buffer for accumulating the numbers, a discard control signal generated by comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold, and a retransmission request threshold for suppressing the accumulation time of each data block in the reception buffer. And a buffer amount monitoring unit that changes
[0044]
Based on the error detection result, the received frame is distinguished into a significant frame that is normally received and an error frame that is not normally received. The reception buffer stores and holds data blocks extracted from the significant frames, and outputs only the data blocks whose order numbers are aligned in order as reception data. That is, when an error frame occurs, data blocks extracted from significant frames received after the error frame are accumulated in the reception buffer until the frame is retransmitted and correctly received. Thereafter, when the retransmission frame is correctly received, the order numbers of the data blocks are aligned for the significant data up to the next error frame, so that these data blocks are output from the reception buffer.
[0045]
The retransmission request buffer receives the sequence number of the error frame, outputs the sequence number of the oldest error frame in which the retransmission frame has not been correctly received, and stores and retains the sequence numbers of the other error frames. That is, when two or more error frames occur, the sequence numbers of other error frames are accumulated in the retransmission request buffer until the first error frame is retransmitted and received correctly. Thereafter, when the first retransmission frame is correctly received, the sequence number of the next error frame is output from the retransmission request buffer.
[0046]
The buffer amount monitoring unit monitors the amount of data stored in the retransmission request buffer, and compares the amount of data with the retransmission request threshold to generate a discard control signal. The reception buffer outputs the stored data block based on the discard control signal without waiting for the retransmission of the preceding error frame. The buffer amount monitoring unit changes the retransmission request threshold so as to suppress the accumulation time of each data block in the reception buffer. For this reason, the output delay of the received data caused by the retransmission can be controlled as needed.
[0047]
According to a second aspect of the present invention, in the data receiving apparatus, the retransmission request buffer is configured to discard the sequence number of the accumulated error frame based on the discard control signal.
[0048]
The data receiving apparatus according to the third aspect of the present invention is configured to output a response confirmation for a significant frame corresponding to a data block stored in the receiving buffer to the data transmitting apparatus based on the discard control signal.
[0049]
The data receiving apparatus according to the present invention includes a FER measuring unit that measures a frame error rate of a received frame, wherein the buffer amount monitoring unit determines a retransmission request threshold based on the frame error rate obtained by the FER measuring unit. Is configured to be changed. When the frame error rate increases, the time from reception of a significant frame to output as received data becomes longer in proportion to the amount of data stored in the retransmission request buffer. Therefore, if the retransmission request threshold is changed based on the frame error rate, it is possible to suppress the delay of the received data.
[0050]
According to a fifth aspect of the present invention, there is provided a data receiving apparatus including a line quality monitoring unit for detecting a line quality of a data communication line, wherein the buffer amount monitoring unit determines a retransmission request based on the line quality obtained by the line quality monitoring unit. It is configured to change the threshold. When the line quality is deteriorated, the time from when a significant frame is received to when it is output as received data becomes longer. Therefore, if the retransmission request threshold is changed based on the channel quality, the delay of the received data can be suppressed.
[0051]
According to a sixth aspect of the present invention, in the data receiving apparatus, the channel quality monitoring unit is configured to measure a received power level, a received power to noise ratio, or a desired received wave power to interference power ratio.
[0052]
The data receiving apparatus according to the present invention according to claim 7, further comprising a received frame number measuring unit for measuring the number of received frames within a predetermined time, and a retransmission request threshold based on the number of received frames obtained by the received frame number measuring unit. Is configured to be changed. If the number of frames to be received changes within a predetermined time, the time from reception of a significant frame to output as received data also changes. Therefore, if the retransmission request threshold is changed based on the number of received frames per predetermined time, it is possible to suppress the delay of the received data.
[0053]
The data receiving apparatus according to the present invention is configured such that the buffer amount monitoring unit changes the retransmission request threshold based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer. Since the line quality, the amount of received data, and the like can be estimated based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer, if the retransmission request threshold is changed based on these data amounts, the received data can be estimated. Can be suppressed.
[0054]
According to a ninth aspect of the present invention, the buffer amount monitoring unit estimates the line quality based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer, and performs retransmission based on the line quality. The request threshold is configured to be changed.
[0055]
In the data receiving apparatus according to the present invention, the buffer amount monitoring unit estimates the received data amount based on the accumulated data amount in the reception buffer and the accumulated data amount in the retransmission request buffer. It is configured to change the retransmission request threshold based on the threshold.
[0056]
A data reception control method according to the present invention is a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame. A reception data accumulation step of accumulating a data block corresponding to a significant frame in a reception buffer until a retransmission frame is received, and accumulating a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame A retransmission request storing step, a FER measuring step of measuring a frame error rate of a received frame, and Suppress the accumulation time of each data block in the receive buffer A threshold determining step for determining a retransmission request threshold, a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold, and outputting a data block stored in the reception buffer from the reception buffer based on a comparison result of the comparison step Receiving data output step.
[0057]
According to a twelfth aspect of the present invention, there is provided a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame. A reception data accumulation step of accumulating a data block corresponding to a significant frame in a reception buffer until a retransmission frame is received, and accumulating a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame A retransmission request accumulation step, a line quality monitoring step for detecting the line quality of the data communication line, and Suppress the accumulation time of each data block in the receive buffer A threshold determining step for determining a retransmission request threshold, a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold, and outputting a data block stored in the reception buffer from the reception buffer based on a comparison result of the comparison step Receiving data output step.
[0058]
A data reception control method according to the present invention is a data reception control method for outputting a retransmission request of an error frame to a data transmitting apparatus based on an error detection result of a reception frame. A reception data accumulation step of accumulating a data block corresponding to a significant frame in a reception buffer until a retransmission frame is received, and accumulating a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame A retransmission request accumulation step, a received frame number measuring step of measuring the number of received frames within a predetermined time, and Suppress the accumulation time of each data block in the receive buffer A threshold determining step for determining a retransmission request threshold, a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold, and outputting a data block stored in the reception buffer from the reception buffer based on a comparison result of the comparison step Receiving data output step.
[0059]
A data reception control method according to the present invention is a data reception control method for outputting a retransmission request for an error frame to a data transmission device based on an error detection result of a reception frame. A reception data accumulation step of accumulating a data block corresponding to a significant frame in a reception buffer until a retransmission frame is received, and accumulating a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame Retransmission request accumulation step, based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer Suppress the accumulation time of each data block in the receive buffer A threshold determining step for determining a retransmission request threshold, a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold, and outputting a data block stored in the reception buffer from the reception buffer based on a comparison result of the comparison step Receiving data output step.
[0060]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram showing one configuration example of the data receiving device according to the first embodiment of the present invention. 9A is a retransmission request buffer unit, and 50 is an FER measurement unit. S6c is frame error information, and s50 is frame error rate information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0061]
The error detector 6 detects an error in the received frame i3 and notifies the FER measuring unit 50 of the presence or absence of the error using the frame error information s6c. The FER measuring unit 50 has a timer function therein, measures an error per unit time occurring in a received frame based on the frame error information s6c, and outputs frame error rate information s50. The retransmission request buffer unit 9A calculates the optimum value of the threshold value set in the retransmission request buffer based on the frame error rate information s50, and determines the threshold value.
[0062]
For example, the frame error rate is compared with a predetermined value, and when the frame error rate exceeds the predetermined value, the retransmission request buffer unit 9A changes the threshold value of the retransmission request buffer to a lower value. Alternatively, when a predetermined number of consecutive frame errors have occurred, the retransmission request buffer unit 9A changes the threshold value of the retransmission request buffer to a lower value. By providing two or more of these predetermined values or predetermined times, the threshold value of the retransmission request buffer can be changed stepwise. Other operations are the same as those in FIG.
[0063]
FIG. 2 is a block diagram showing a detailed configuration of the retransmission request buffer unit 9A of FIG. 34A in the figure is a buffer amount monitoring unit. S50 is frame error rate information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0064]
The buffer amount monitoring unit 34A calculates the optimum value of the threshold value set in the retransmission request buffer based on the frame error rate information s50, and notifies the read control unit 32 of the calculated threshold value. The buffer amount monitoring unit 34A monitors the number of retransmission requests stored in the buffers 331 to 33n, and when the number of retransmission requests exceeds the threshold value of the retransmission request buffer calculated based on the frame error rate information s50, the buffer is monitored. Stop all stored retransmission requests. More specifically, read control information s34 is output, and the read operation of read control unit 32 is stopped. Other operations are the same as those shown in the figure, and a description thereof will be omitted.
[0065]
Next, a basic concept of a method of setting a threshold value of the retransmission request buffer unit 9A and a control method according to the present embodiment will be described with reference to FIGS. FIG. 3 is a timing chart showing an example of the operation of the data receiving apparatus of FIG. 1, and is a control example in a case where a frame error continues for a relatively short period. In the figure, (a) shows the received frame i3, (b) shows the data stored in the reception buffers 251 to 25n, (c) shows the threshold value of the retransmission request buffer, (d) shows the data stored in the retransmission request buffers 331 to 33n, and (e). ) Is the received data s7a. Further, f1 to f6 in the drawing each indicate a received frame, and an X mark below the received frame i3 indicates that an error has occurred in the received frame.
[0066]
In FIG. 3, the threshold value of the retransmission request buffer is set to 3. Since the received frame f1 (sequence number 1) is received without error, it is output as received data as it is. Since the received frames f2 (sequence number 2), f3 (sequence number 3) and f4 (sequence number 4) are erroneously received, the data receiving apparatus uses the backward channel to retransmit the frame. Request for. At this time, since the retransmission request is made in order from the oldest unreceived frame, a retransmission request for the frame of sequence number 2 is made first, and sequence numbers 3 and 4 are stored in the retransmission request buffer.
[0067]
Thereafter, the received frame f5 of the frame number 5 received without error is stored in the reception buffer until the sequence numbers are correctly aligned. When the retransmission frame f6 of the frame of sequence number 2 for which retransmission has been requested is received without error, the received data 2 is output and a request is made to retransmit the frame of sequence number 3, which is the oldest unreceived frame in the retransmission request buffer. Hereinafter, the same operation is performed. Here, before the frame of frame number f5 (order number 5) is output as received data, re-transmission of received frames f2 (order number 2), f3 (order number 3) and f4 (order number 4) A delay equivalent to 10 received frames has occurred. However, in this case, all frames can be received without error by retransmission control.
[0068]
FIG. 4 is a timing chart showing another example of the operation of the data receiving apparatus of FIG. 1, and shows a control example in a case where the threshold of the retransmission request buffer is fixed when frame errors continue for a relatively long period. FIG. In the figure, f1 indicates a received frame, and an X mark below the received frame i3 indicates that an error has occurred in the received frame.
[0069]
In FIG. 4 as well, the threshold value of the retransmission request buffer is set to 3 as in FIG. The control and operation in FIG. 4 are the same as those in FIG. Here, a delay corresponding to 11 received frames has occurred before the frame f1 of the frame number 6 is output as received data. As described above, when the frame error continues for a relatively long period, the delay that occurs until a subsequent frame is output as received data increases in proportion to the amount of data stored in the retransmission request buffer.
[0070]
FIG. 5 is a timing chart showing another example of the operation of the data receiving apparatus in FIG. 1, which illustrates an operation when the threshold value of the retransmission request buffer is lowered when a frame error continues for a relatively long period. FIG. In the figure, f1 indicates a received frame, and an X mark below the received frame i3 indicates that an error has occurred in the received frame.
[0071]
In FIG. 5, the threshold value of the retransmission request buffer is set to 2. The control and operation in FIG. 5 are the same as those in FIG. 3 and FIG. Here, in FIG. 5, since the retransmission request buffer is set to a low threshold value, the retransmission request for an error that has occurred until the reception frame f1 having the sequence number 6 is received is stopped. There is no delay from the reception of the received frame to the output as the received data. As described above, by adopting a data receiving apparatus configuration in which the threshold value of the retransmission request buffer is made variable in accordance with the frame error rate, it is possible to control delay and errors remaining in received data in accordance with changes in wireless channel conditions.
[0072]
In the present embodiment, as an example, the control method of setting the threshold value of the retransmission request buffer low when the period during which the error continues is long has been described. The control method of setting the threshold value of the retransmission request buffer to be higher as the period during which is repeated is longer.
[0073]
Embodiment 2 FIG.
In the first embodiment, the configuration of the device when the frame error rate is used has been described as a method for detecting the state of the wireless channel. However, the device configuration for detecting the wireless channel state by monitoring the channel quality may be used. . The line quality includes, for example, a reception power level, a reception power-to-noise ratio, a reception desired-wave power-to-interference power ratio, and the like. The reception power noise ratio is a ratio between a reception signal level and an unnecessary signal level generated by an amplifier or the like in the reception apparatus.The reception desired wave power to interference power ratio is a reception signal level from a predetermined communication partner. , And other received signal levels (for example, signal levels of unintended communications between third parties).
[0074]
FIG. 6 is a block diagram showing one configuration example of the data receiving device according to the second embodiment of the present invention. In the figure, reference numeral 51 denotes a line quality monitoring unit, and 9A denotes a retransmission request buffer unit. In addition, i4 is a radio line state signal, and s51 is line quality information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG. The wireless channel status signal i4 is a signal obtained by determining the quality of the channel quality.
[0075]
The channel quality monitoring unit 51 monitors the radio channel quality based on the radio channel status signal i4, and when there is a change in the radio channel quality, notifies the retransmission request buffer unit 9A using the channel quality information s51. The retransmission request buffer unit 9A calculates the optimum value of the threshold value set in the retransmission request buffer based on the channel quality information s51, and determines the threshold value. The other operations are the same as those in FIG. In addition, the configuration and operation of the retransmission request buffer unit 9A are the same as those in the first embodiment, and a description thereof will be omitted.
[0076]
Also, in the present embodiment, similarly to the first embodiment, a control method for lowering the threshold of the retransmission request buffer to prevent an increase in delay, and in the case of data requiring a high error rate, errors continue. The device configuration is such that a control method of setting the threshold value of the retransmission request buffer higher as the period becomes longer is possible.
[0077]
In the present embodiment, the threshold of the retransmission request buffer is determined by monitoring the received power level, the received power to noise ratio, the desired received signal power to interference power ratio, and the like as the channel quality. Therefore, compared to the first embodiment, it is possible to detect a change in the state of the wireless channel in a shorter time and change the threshold value of the re-request buffer.
[0078]
Embodiment 3 FIG.
In the first embodiment, the frame error rate is measured by the FER measuring unit 50 to detect a change in the line state, and the threshold value of the retransmission request buffer of the retransmission request buffer unit 9A is made variable. A configuration may be adopted in which a change in the line state is detected from the number of data stored and the number of data stored in the reception buffer, and the threshold value of the retransmission request buffer is made variable.
[0079]
FIG. 7 is a block diagram showing one configuration example of the data receiving device according to the third embodiment of the present invention. In the figure, 7A is a reception buffer unit, and 9B is a retransmission request buffer unit. S7b is the reception buffer storage data amount information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0080]
The reception buffer unit 7A outputs the number of data stored in the block as the reception buffer storage data amount information s7b. The retransmission request buffer unit 9B determines the threshold of the retransmission request buffer from the reception buffer storage data amount information s7b and the amount of data stored in the block.
[0081]
FIG. 8 is a block diagram showing a detailed configuration of the retransmission request buffer unit 9B of FIG. 34B in the figure is a buffer amount monitoring unit. S7b is the reception buffer storage data amount information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG. The buffer amount monitoring unit 34B detects the line state from the number of retransmission request data stored in the block and the reception buffer storage data amount information s7b, and sets a threshold value of the retransmission request buffer.
[0082]
For example, the sum of the amount of data stored in the receiving buffer and the amount of data stored in the block is compared with a predetermined value, and if the total amount of data exceeds the predetermined value, the retransmission request buffer 9B sets the threshold of the retransmission request buffer to Change to a lower value. By providing two or more of the predetermined values, the threshold value of the retransmission request buffer may be changed stepwise. The other operations are the same as those in FIG.
[0083]
FIG. 9 is a timing chart showing an example of the operation of the data receiving device of FIG. Using this figure, the buffer amount monitoring unit 34B detects the line state from the number of retransmission request data stored in the retransmission request buffer unit 9B and the reception buffer storage data amount information s7b output by the reception buffer unit 7A. The method will be described. In addition, similarly to FIGS. 3 to 5, an X mark below the received frame i3 indicates that an error has occurred in the received frame.
[0084]
When errors do not occur continuously as in section A in the figure, the number of retransmission request data stored in the retransmission request buffer is small. On the other hand, when errors occur consecutively as in section C, the number of retransmission request data stored in the retransmission request buffer increases, so that it is determined that errors occur in a burst (continuous) manner. can do. If an error-free section continues after an error, such as section B and section D, the number of data stored in the reception buffer increases, so that it is determined that the line state has recovered. Can be. The method of setting the threshold value of the retransmission request buffer after detecting the line state is the same as in the first embodiment, and a description thereof will not be repeated.
[0085]
Also in the present embodiment, as in Embodiment 1, a control method for lowering the threshold of the retransmission request buffer to prevent an increase in delay, and an error in the case of data with a severe error rate requirement, The device configuration is such that a control method for setting the threshold value of the retransmission request buffer higher as the continuous period becomes longer is possible.
[0086]
In the present embodiment, unlike the first embodiment or the second embodiment, it is not necessary to add a new block having the function to the configuration for detecting the line state. It can be realized by.
[0087]
Embodiment 4 FIG.
In the first to third embodiments, the configuration is such that the threshold value of the retransmission request buffer is variable depending on the line state. However, the configuration may be such that the threshold value of the retransmission request buffer is variable depending on the amount of data received by the receiving device of the data transmission device. .
[0088]
FIG. 10 is a block diagram showing one configuration example of the data receiving device according to the fourth embodiment of the present invention. In the figure, reference numeral 52 denotes a reception data amount measurement unit, and 9C denotes a retransmission request buffer unit. S52 is reception data amount information. The other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0089]
The reception data amount measuring unit 52 measures the reception data amount to be received within a predetermined time from the reception frame i3, and outputs the reception data amount information s52. The retransmission request buffer unit 9C determines a threshold value of the reception request buffer based on the reception data amount information s52.
[0090]
For example, the number of frames received per unit time is compared with a predetermined value, and when the number of frames exceeds the predetermined value, the retransmission request buffer 9C changes the threshold value of the retransmission request buffer to a lower value. By providing two or more of the predetermined values, the threshold value of the retransmission request buffer may be changed stepwise.
[0091]
FIG. 11 is a timing chart showing an example of the operation of the data receiving apparatus of FIG. 10, and is a diagram for explaining a problem of the conventional data receiving apparatus when the number of received frames is small. Control of the threshold value of the retransmission request buffer based on the amount of received data will be described with reference to FIG. As in FIGS. 3 to 5, an X mark below the received frame i3 indicates that an error has occurred in the received frame.
[0092]
As shown in FIG. 11, when the number of received frames received within a predetermined time is small, the threshold value of the retransmission request buffer must be exceeded because the amount of data stored in the retransmission request buffer is small even if the radio link condition is poor. Is reduced. For this reason, retransmission is stopped, and a frame that has been received without error cannot be output as received data, thereby increasing delay. In FIG. 11, for example, a frame corresponding to sequence number 4 has a delay equivalent to 10 received frames.
[0093]
FIG. 12 is a timing chart showing another example of the operation of the data receiving device in FIG. 10, and is a diagram for explaining the operation according to the present embodiment. This figure shows the operation when the threshold of the retransmission request buffer is set to 0 when the same error as in FIG. 11 occurs. As shown in FIG. 12, when the number of received frames received within a predetermined time is small, by lowering the threshold value of the retransmission request buffer, it is possible to suppress the occurrence of delay. In FIG. 12, for example, no delay occurs in the frame of the sequence number 4.
[0094]
In the present embodiment, an example in which the threshold value of the retransmission request buffer is reduced when the number of received frames received within a predetermined time is small has been described. If the number of received frames received in a long time is large, retransmission may affect a subsequent frame with a delay, and in such a case, the threshold value of the retransmission request buffer can be lowered.
[0095]
Further, in the present embodiment, the method of controlling the threshold value of the retransmission request buffer according to the number of received frames received within a predetermined time has been described. It is also possible to combine with the method of controlling the threshold value of the retransmission request buffer according to the line state described in 1 to 3.
[0096]
Embodiment 5 FIG.
In the fourth embodiment, the number of frames to be received within a predetermined time is measured by the received data amount measuring unit 52, and the threshold value of the retransmission request buffer is made variable. However, it is stored in the retransmission request buffer. A configuration may be adopted in which the number of frames to be received within a predetermined time is estimated from the number of data and the number of data stored in the reception buffer, and the threshold value of the retransmission request buffer is made variable.
[0097]
FIG. 13 is a block diagram showing one configuration example of the data receiving device according to the fifth embodiment of the present invention. 9D in the figure is a retransmission request buffer unit. Other blocks and signals are the same as or equivalent to those of the same reference numerals described in FIG.
[0098]
The retransmission request buffer unit 9D calculates the number of reception frames to be received within a predetermined time based on the reception buffer storage data amount information s7b output by the reception buffer unit 7A and the data amount stored in the retransmission request buffer in the own block. Is calculated to control the threshold value of the retransmission request buffer. The control method is the same as in the fourth embodiment, and a description thereof will not be repeated.
[0099]
In the present embodiment, an example is shown in which the threshold value of the retransmission request buffer is lowered when the number of received frames to be received within a predetermined time is small, If the number of received frames received in a long time is large, retransmission may affect a subsequent frame with a delay, and in such a case, the threshold value of the retransmission request buffer can be lowered.
[0100]
Further, in the present embodiment, the method of controlling the threshold value of the retransmission request buffer based on the number of received frames received within a predetermined time has been described. It is also possible to combine with the method of controlling the threshold value of the retransmission request buffer according to the line state described in 1 to 3.
[0101]
In the present embodiment, as in Embodiment 4, in order to measure the number of received frames received within a predetermined time, it is not necessary to add a block having the function to the configuration. The function can be realized with a simple configuration.
[0102]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the output delay of received data can be suppressed in the data receiver which outputs the retransmission request | requirement of an error frame with respect to a data transmitter based on the error detection result of a received frame. That is, a reception buffer that stores a data block corresponding to a significant frame until a retransmission frame is received for a preceding error frame, and a retransmission request that stores the sequence number of another error frame until a retransmission frame is received for the preceding error frame. In a data receiving apparatus including a buffer and a buffer amount monitoring unit that generates a discard control signal by comparing the amount of data stored in the retransmission request buffer with a retransmission request threshold, the buffer monitoring unit changes the retransmission request threshold. In addition, the accumulation time of each data block in the reception buffer can be suppressed.
[0103]
Further, according to the present invention, by changing the number of retransmission request thresholds depending on the line state, it is possible to control delay and errors remaining in the received data according to changes in the wireless line condition.
[0104]
Further, according to the present invention, by changing the retransmission request threshold according to the number of frames received per unit time, it is possible to control delay and errors remaining in received data for a service with a variable data amount.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a data receiving device according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a detailed configuration of a retransmission request buffer unit 9A in FIG.
FIG. 3 is a timing chart showing an example of the operation of the data receiving device of FIG. 1, and is a diagram for explaining the operation when a continuous frame error occurs in a relatively short period.
FIG. 4 is a timing chart showing another example of the operation of the data receiving apparatus of FIG. 1, in the case where a continuous error of a frame occurs in a relatively long period and the threshold value of a retransmission request buffer is fixed. FIG.
FIG. 5 is a timing chart showing another example of the operation of the data receiving device of FIG. 1, illustrating the operation when the threshold value of the retransmission request buffer is lowered when frame errors continue for a relatively long period. FIG.
FIG. 6 is a block diagram showing a configuration example of a data receiving device according to a second embodiment of the present invention.
FIG. 7 is a block diagram showing a configuration example of a data receiving device according to a third embodiment of the present invention.
FIG. 8 is a block diagram showing a detailed configuration of a retransmission request buffer unit 9B of FIG. 7;
FIG. 9 is a timing chart showing an example of the operation of the data receiving device of FIG. 7;
FIG. 10 is a block diagram showing a configuration example of a data receiving device according to a fourth embodiment of the present invention.
11 is a timing chart showing an example of the operation of the data receiving apparatus of FIG. 10, and is a diagram for explaining a problem of the conventional data receiving apparatus when the number of received frames is small.
12 is a timing chart showing another example of the operation of the data receiving device in FIG. 10, and is a diagram for explaining the operation according to the present embodiment.
FIG. 13 is a block diagram showing a configuration example of a data receiving device according to a fifth embodiment of the present invention.
FIG. 14 is a timing chart schematically showing the basic operation of ARQ.
FIG. 15 is a block diagram showing a configuration example of a conventional general data transmission device (ARQ transmission device).
FIG. 16 is a block diagram showing a configuration example of a conventional general data receiving apparatus (ARQ receiving apparatus).
FIG. 17 is a block diagram showing a detailed configuration example of a transmission buffer unit (transmission buffer unit 2 in FIG. 15) of a conventional data transmission device.
18 is a timing chart showing an example of the operation of the transmission buffer unit 2 of FIG. 17, and is a diagram for explaining a delay occurring in the transmission buffer unit of the conventional data transmission device.
FIG. 19 is a block diagram showing a detailed configuration example of a reception buffer unit (reception buffer unit 7L in FIG. 16) of the conventional data reception device.
20 is a timing chart illustrating an example of the operation of the reception buffer unit 7L of FIG. 19, and is a diagram for describing a delay generated in the reception buffer unit of the conventional data receiving device.
FIG. 21 is a block diagram showing a detailed configuration example of a retransmission request buffer unit (retransmission request buffer unit 9L in FIG. 16) of the conventional data receiving apparatus.
FIG. 22 is a timing chart showing an example of the operation of the entire conventional general data receiving apparatus (ARQ receiving apparatus in FIG. 16), and is a diagram for explaining a delay caused by an increase in retransmission requests.
FIG. 23 is a block diagram showing another configuration example of the conventional data receiving apparatus, and is a diagram for explaining a retransmission stop function described in Japanese Patent Application Laid-Open No. 11-88466.
24 is a block diagram showing a detailed configuration example of a retransmission request buffer unit (retransmission request buffer unit 9 in FIG. 23) of a conventional data receiving apparatus having a retransmission stop function.
FIG. 25 is a block diagram showing a detailed configuration example of a reception buffer unit (reception buffer unit 7 in FIG. 23) of a conventional data reception device having a retransmission stop function.
26 is a timing chart showing an example of the operation of the entire conventional data receiving apparatus having the retransmission stop function (ARQ receiving apparatus in FIG. 23), showing the operation when an error under the same conditions as in FIG. 22 occurs; Have been.
[Explanation of symbols]
1 retransmission request determination unit, 2 transmission buffer unit, 3 transmission processing unit,
4 retransmission buffer section, 5 OR operation section, 6 error detection section,
7, 7A, 7L reception buffer unit, 8, 8L sequence number storage unit,
9, 9A to 9D, 9L retransmission request buffer, 10 backward signal generation unit,
11 data division unit, 12 write control unit, 13 read control unit,
141 to 14n transmission buffer, 21 data extraction unit, 22 write control unit,
23, 23L read control unit, 24 sequence number storage unit,
251 to 25n reception buffer, 31 write control unit, 32 read control unit,
331-33n retransmission request buffer,
34, 34A, 34B buffer amount monitoring unit, 50 FER measuring unit,
51 line quality monitoring unit, 52 reception data amount measurement unit,
d1 to d3 data blocks, f1 to 6 received frames,
i1 backward signal, i2 generated data, i3 received frame,
i4 wireless channel status signal, s1 retransmission request signal, s11 data block,
s12a buffer start position information, s12b write position information,
s13 read position information, s2 generated data block,
s21a significant frame number, s21b data block,
s22b write position information, s23 read position information,
s24 output frame number, s3 generated frame,
s31a buffer start position information, s31b write position information,
s32 read position information, s34 read control information, s4 retransmission frame,
s5 transmission frame, s50 frame error rate information, s51 line quality information,
s52 received data amount information, s6a significant frame,
s6b error detection sequence number, s6c frame error information,
s7a reception data, s7b reception buffer storage data amount information,
s8 Response confirmation sequence number, s9a retransmission request sequence number, s9b discard sequence number.

Claims (14)

Based on the error detection result of the received frame, in the data receiving device that outputs a request for retransmission of an error frame to the data transmitting device, while storing a data block corresponding to a significant frame until a retransmission frame is received for a preceding error frame, A reception buffer that outputs a data block stored based on a discard control signal, a retransmission request buffer that stores the sequence number of another error frame until a retransmission frame is received for a preceding error frame, and data stored in the retransmission request buffer A buffer amount monitoring unit that generates a discard control signal by comparing the amount with the retransmission request threshold value and changes the retransmission request threshold value so as to suppress the accumulation time of each data block in the reception buffer. Data receiver. 2. The data receiving apparatus according to claim 1, wherein the retransmission request buffer discards the sequence number of the error frame stored based on the discard control signal. 2. The data receiving device according to claim 1, wherein a response confirmation is output to the data transmitting device for a significant frame corresponding to the data block stored in the receiving buffer, based on the discard control signal. 3. The apparatus according to claim 1, further comprising an FER measuring unit for measuring a frame error rate of a received frame, wherein the buffer amount monitoring unit changes a retransmission request threshold based on the frame error rate obtained by the FER measuring unit. Or the data receiving device according to 3. 2. The communication system according to claim 1, further comprising a line quality monitoring unit that detects a line quality of the data communication line, wherein the buffer amount monitoring unit changes a retransmission request threshold based on the line quality obtained by the line quality monitoring unit. 4. The data receiving device according to 2 or 3. 6. The data receiving apparatus according to claim 5, wherein the channel quality monitoring unit measures a received power level, a received power to noise ratio, or a desired received signal power to interference power ratio. 3. The apparatus according to claim 1, further comprising a reception frame number measurement unit that measures the number of reception frames within a predetermined time, wherein the retransmission request threshold is changed based on the reception frame number obtained by the reception frame number measurement unit. 4. The data receiving device according to any one of 3. 4. The data receiving apparatus according to claim 1, wherein the buffer amount monitoring unit changes the retransmission request threshold based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer. 9. The system according to claim 8, wherein the buffer amount monitoring unit estimates line quality based on the amount of data stored in the reception buffer and the amount of data stored in the retransmission request buffer, and changes the retransmission request threshold based on the line quality. The data receiving device according to claim 1. The buffer amount monitoring unit estimates a received data amount based on a stored data amount in a reception buffer and a stored data amount in a retransmission request buffer, and changes a retransmission request threshold based on the received data amount. Item 9. The data receiving device according to item 8. In a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame, a data block corresponding to a significant frame is stored in a reception buffer until a retransmission frame is received for a preceding error frame. A receiving data storing step of storing, a retransmission request storing step of storing the sequence number of another error frame in a retransmission request buffer until a retransmission frame of the preceding error frame is received, and an FER measurement for measuring a frame error rate of the received frame Step, a threshold determining step of determining a retransmission request threshold so as to suppress the accumulation time of each data block in the reception buffer based on the frame error rate, and a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold And the comparison result of the comparison step Data reception control method is characterized in that a reception data output step of outputting from the reception buffer the stored data blocks in the reception buffer based on. In a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame, a data block corresponding to a significant frame is stored in a reception buffer until a retransmission frame is received for a preceding error frame. A receiving data storing step of storing, a retransmission request storing step of storing a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame, and a line quality detecting a line quality of a data communication line A monitoring step, a threshold determination step of determining a retransmission request threshold so as to suppress the accumulation time of each data block in the reception buffer based on the line quality, and a comparison comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold Step and the comparison result of the comparison step Data reception control method characterized in that the stored data blocks in the reception buffer and a reception data output step of outputting from the receive buffer Hazuki. In a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame, a data block corresponding to a significant frame is stored in a reception buffer until a retransmission frame is received for a preceding error frame. A receiving data storing step of storing, a retransmission request storing step of storing a sequence number of another error frame in a retransmission request buffer until a retransmission frame of the preceding error frame is received, and measuring the number of received frames within a predetermined time A number-of-received-frames measuring step; a threshold determining step of determining a retransmission request threshold so as to suppress the accumulation time of each data block in the reception buffer based on the number of received frames; A comparison step to compare with the ratio Data reception control method characterized in that the stored data blocks in the reception buffer based on the comparison result in step with the reception data output step of outputting from the receive buffer. In a data reception control method for outputting a retransmission request of an error frame to a data transmission device based on an error detection result of a reception frame, a data block corresponding to a significant frame is stored in a reception buffer until a retransmission frame is received for a preceding error frame. A receiving data storing step of storing, a retransmission request storing step of storing a sequence number of another error frame in a retransmission request buffer until a retransmission frame is received for a preceding error frame, a storage data amount in the reception buffer and a retransmission request buffer A threshold determining step of determining a retransmission request threshold so as to suppress the storage time of each data block in the reception buffer based on the amount of data stored in the buffer, and a comparing step of comparing the amount of data stored in the retransmission request buffer with the retransmission request threshold. , Based on the comparison result of the comparison step Data reception control method is characterized in that a reception data output step of outputting from the reception buffer the stored data blocks in the transmit buffer.

Images